The family of a healthy woman who collapsed during the London Marathon has called for tighter regulation of health supplements after hearing that an "amphetamine-like" substance in one she used probably led to her death.

Claire Squires, 30, a keen runner, collapsed a mile from the finish line on April 22 last year. The hairdresser, from North Kilworth, Leicestershire, suffered cardiac failure and was dead within two hours, an inquest at Southwark Coroner's Court heard.

She bought the supplement Jack3D online but did not realise it contained 1,3-dimethylamine (DMAA), which increases heart rate, the court heard.

Boyfriend Simon van Herrewege told the hearing Miss Squires put a scoop in her water bottle for a boost if she needed it during her charity run for the Samaritans. Outside court he read a statement on behalf of the family.

"Claire would never ever have taken anything that would cause her harm, or even worse risk her life. She innocently took a supplement which at the time was entirely legal and widely available on the high street, and somewhat worryingly apparently used by so many others.

"It is clear that there needs to be far better supervision of the so-called health foods and supplements industry so that no more tragedies like this happen again, causing other families to have to go through what we have been through this past year.

"Claire was a beautiful person committed to helping others. We have been comforted by all those who knew and loved Claire and by the heart-warming support shown by the general public through donations to the Samaritans and subsequent charitable events to raise money for worthwhile causes in her name.

"The overwhelming response will help Claire's memory live on and hopefully help others."

Coroner Dr Philip Barlow issued a similar warning: "My hope is that the coverage of this case and the events leading up to Claire's death will help publicise the potentially harmful effects of DMAA during extreme exertion."

In a narrative verdict he ruled: "She had taken a supplement containing DMAA which on the balance of probabilities in combination with extreme physical exertion caused acute cardiac failure which resulted in her death."